Both have good and bad qualities, I've been with both providers, and am currently with T-mobile. It really matters what you are looking for.
I've actually had MORE dropped calls when I had Verizon, I'm not sure if it's my phone, or whatever. You will have dropped calls no matter WHAT service provider you have... so it's best time to get used to that... it's horrid, but it's the truth D: Each provider will promise low dropped calls, but sometimes... you just get in a bad call zone, and you can't help it.
Verizon
PROS:
Price of plans, few dropped calls, and reception:
Price wise, for plans, Verizon is a good choice IMO. I was paying about $50 compared to my $80 now, but I had about 900 minutes, with a small 200 text package. It wasn't bad for the price, but everyone is different.
I had few dropped calls, but it seems again that I had more than T-Mobile now.
Reception, ANYWHERE BUT MY HOUSE... was good. In my house I had no reception, which was another reason I changed over to T-Mobile.
CONS:
Horrible customer service, bad warranty packages, and horrid reception in my house 8D
The customer service with Verizon, in my opinion, was horrible. Everytime something happened with my phone, which seemed to happen frequently, I would call, and always seem to get someone snotty, or just plain unhelpful! They're rules are whack too.
Bad warranties for phones, they would continually tell me that they couldn't swap out my phone for a refurbished one because they believed I had water damage? Even though I had checked the phone before it left my hands, and the little stickers were ALL white. So I would constantly be fighting them on that, with the horrid customer service. Ugh.
Again, Horrid Reception from my house.
T-Mobile, I actually switched to T-Mobile from Verizon.
PROS:
Amazing customer service, good choices of phones, and great reception.
Amazing customer service, I can't even tell you how helpful and kind the people are at T-Mobile. @_@ I love them <3 <3 Mucho, because they are so kind, they help you with your problem with no rudeness whatsoever. You sometimes get a bad egg, don't get me wrong, BUT, as long as you are nice, they are
I feel that T-Mobile has a better choice of phones, and for much better prices. I originally switched over to T-Mobile, for the sidekick lx D: And I have no chance of ever switching back to any other carrier... because the sidekick lx is my holy grail phone. Some people feel this way as well, some don't. But in price ranges and selection, I think T-Mobile is pretty reached on that.
T-Mobile has great reception for me, once in a great while my sidekick data will go out, and sometimes it will flip out on me, but I think that's the sidekick as a whole, because it's data is on a different frequency... or something like that.
CONS:
KINDAAAA pricey plans, dropped calls occasionally, and no mobile to mobile or anything I think...
The plans are KINDA pricey... I pay $80 now for unlimited txt, pic msging, data and email. Plus 5 my faves and 300 minutes on Flexpay. I don't really call much though... I really text a lot and use my data... so it's not SO bad for me. But $80 a month IS kinda pricey for some people. Again, this isn't ALL plans, just mine in general. And this is the cheapest I could get for my sidekick...
Dropped calls occasionally, no where near as many as I had with Verizon, AT&T, US Cellular or Sprint, but not bad at all.
I do not believe they have mobile to mobile... but I might be mistaken @_@ So don't fully quote me on that.
THE BEST thing to do, is to research exactly what you want, find a carrier who has good customer service, I'd personally stay away from Verizon, Sprint and AT&T because I find them rude on all parts because IMO, it's because they have hundreds of millions of customers, where as T-Mobile has something in the 10-15 million range. I personally like quality over quantity. But it's really up to you
Hope this helped in the least bit